this is evil you should be using XDG paths on linux, appdata on windows, and whatever the hell mac does on mac
This is one of those problems that tests wisdom more than intelligence.
typedef struct {
uint64_t metadata;
void* data;
} tagged_ptr;
tagged_ptr my_func(/* ... */);
For the record, mac's equivalent is typically
~/Library/Application Support. If not there, CLI apps will often just check ~/.config.As would most languages, I'm sure.
(define libSDL3 (load-shared-object "libSDL3.so.0"))
(define init-sdl (foreign-procedure "SDL_Init" (int) boolean))
(define create-window (foreign-procedure "SDL_CreateWindow" (string int int int) uptr))
(define create-renderer (foreign-procedure "SDL_CreateRenderer" (uptr uptr) uptr))
(define SDL-INIT-VIDEO 32)
(init-sdl SDL-INIT-VIDEO)
(define *window* (create-window "Hello Chez" 640 400 0))
(define *renderer* (create-renderer *window* 0))
(define-ftype sdl-rect
(struct
[x float]
[y float]
[w float]
[h float]))
(define (make-sdl-rect x y w h)
(let
([ptr (make-ftype-pointer
sdl-rect (foreign-alloc (ftype-sizeof sdl-rect)))])
(ftype-set! sdl-rect (x) ptr x)
(ftype-set! sdl-rect (y) ptr y)
(ftype-set! sdl-rect (w) ptr w)
(ftype-set! sdl-rect (h) ptr h)
ptr))
(define (render-rect rect)
((foreign-procedure "SDL_SetRenderDrawColor"
(uptr unsigned-8 unsigned-8 unsigned-8 unsigned-8) boolean)
*renderer* 255 255 255 255)
((foreign-procedure "SDL_RenderFillRect"
(uptr (* sdl-rect)) boolean)
*renderer* rect))
(render-rect (make-sdl-rect 300.0 180.0 20.0 20.0))
((foreign-procedure "SDL_RenderPresent" (uptr) boolean) *renderer*)
I think Guile also has the same sort of dlopen, live ffi. Pretty neat to be able to mess with this stuff live in the repl without a compilation step. Although one downside is, as you see, you don't have the easiest access to #define'd constants.
iiuc gambit just lets you put c snippets in your code that can #include but the catch is that they need to be compiled before you can use them in the repl
Yeah, I'm doing something like that with my current Chicken project.
(foreign-declare "#include <SDL3/SDL.h>")
(define SDL_INIT_AUDIO (foreign-value "SDL_INIT_AUDIO" unsigned-integer32))
(define SDL_INIT_VIDEO (foreign-value "SDL_INIT_VIDEO" unsigned-integer32))
(define SDL_INIT_JOYSTICK (foreign-value "SDL_INIT_JOYSTICK" unsigned-integer32))
(define SDL_INIT_HAPTIC (foreign-value "SDL_INIT_HAPTIC" unsigned-integer32))
(define SDL_INIT_GAMEPAD (foreign-value "SDL_INIT_GAMEPAD" unsigned-integer32))
(define SDL_INIT_EVENTS (foreign-value "SDL_INIT_EVENTS" unsigned-integer32))
(define SDL_INIT_SENSOR (foreign-value "SDL_INIT_SENSOR" unsigned-integer32))
(define SDL_INIT_CAMERA (foreign-value "SDL_INIT_CAMERA" unsigned-integer32))
(define SDL_Init (foreign-lambda bool SDL_Init unsigned-integer32))
(define SDL_InitSubSystem (foreign-lambda bool SDL_InitSubSystem unsigned-integer32))
(define SDL_Quit (foreign-lambda void SDL_Quit))
(define SDL_QuitSubSystem (foreign-lambda void SDL_QuitSubSystem unsigned-integer32))
(define SDL_GetError (foreign-lambda c-string SDL_GetError))foreign-lambda*, which you can write a C function and supply the body as a string literal.SDL_Event accessors look like this:(define SDL_Event-type
(foreign-lambda* unsigned-integer32 ((u8vector ev))
"C_return(((SDL_Event*)ev)->type);"))
(define SDL_Event-motion-xrel
(foreign-lambda* float ((u8vector ev))
"C_return(((SDL_Event*)ev)->motion.xrel);"))
(define SDL_Event-motion-yrel
(foreign-lambda* float ((u8vector ev))
"C_return(((SDL_Event*)ev)->motion.yrel);"))SDL_Events as byte buffers (u8vectors) on the Chicken side. Other SDL data types (like if I was using SDL_Surfaces), I'd let SDL itself allocate them and just handle them as pointers, but SDL_Events are entirely self contained so they're a good candidate for garbage collection.C_return is just a C macro for return, but Chicken's compiler implementation does some clever/funky stuff, so you need to use the special macro for stack cleanup before turning to Scheme code. But as far as I need to be concerned, it's just return.SDL_Event struct is a huge union with a bajillion members for all the different event types. I only have those three accessors defined right now. At some point I might throw together some shell scripts and see if I can generate all the accessors. But for now, I'm just defining the ones I need by hand as I find a need for them.
yeah this is almost exactly like the other scheme->c compilers down to needing a weird macro to return from the function
you might just need to make the syntax yourself with whatever chicken's local syntax-case substitute is
I was going to just grep the headers and fuck around with sed until I got something workable and then edit it by hand but this is a far better approach.
;; ok syntax
;; (define-SDL_Event-getter return-type (foo bar))
;; =>
;; (define SDL_Event-foo-bar
;; (foreign-lambda* return-type ((u8vector ev))
;; "C_return(((SDL_Event*)ev)->foo.bar);"))
(define-syntax define-SDL_Event-getter
(er-macro-transformer
(lambda (exp rename compare)
(import (srfi-1)
(srfi-2)
(srfi-13)
(chicken string)
(chicken foreign)
(chicken format))
(or (and-let* ((_ (and (list? exp)
(= (length exp) 3)))
(_ (car exp))
(return-type (and (symbol? (cadr exp))
(cadr exp)))
(member-path (and (list? (caddr exp))
(every symbol? (caddr exp))
(caddr exp)))
(member-path-c (string-join (map ->string member-path) "."))
(member-path-scm (string->symbol
(string-join
(map ->string member-path) "-")))
;; renames
(&define (rename 'define))
(&foreign-lambda* (rename 'foreign-lambda*))
(scheme-identifier
(string->symbol (format "SDL_Event-~a" member-path-scm)))
(c-body-string
(format "C_return(((SDL_Event*)ev)->~a);" member-path-c)))
`(,&define ,scheme-identifier
(,&foreign-lambda* ,return-type ((u8vector ev))
,c-body-string)))
(error "bad define-SDL_Event-getter syntax" exp)))))#;2> (expand '(define-SDL_Event-getter return-type (foo bar)))
; loading /usr/lib/chicken/11/srfi-13.so ...
; loading /usr/lib/chicken/11/srfi-14.so ...
(##core#begin (##core#ensure-toplevel-definition SDL_Event-foo-bar) (##core#set! SDL_Event-foo-bar (foreign-lambda*62 return-type ((u8vector ev)) "C_return(((SDL_Event*)ev)->foo.bar);")))(define-foreign-type SDL_MouseID unsigned-int32)
(define-foreign-type SDL_MouseButtonFlags unsigned-int32)
(define-foreign-type Uint8 unsigned-byte)
(define-SDL_Event-getter SDL_WindowID (motion windowID))
(define-SDL_Event-getter SDL_MouseID (motion which))
(define-SDL_Event-getter SDL_MouseButtonFlags (motion state))
(define-SDL_Event-getter float (motion x))
(define-SDL_Event-getter float (motion y))
(define-SDL_Event-getter float (motion xrel))
(define-SDL_Event-getter float (motion yrel))
(define-SDL_Event-getter SDL_WindowID (button windowID))
(define-SDL_Event-getter SDL_MouseID (button which))
(define-SDL_Event-getter Uint8 (button button))
(define-SDL_Event-getter bool (button down))
(define-SDL_Event-getter Uint8 (button clicks))
(define-SDL_Event-getter float (button x))
(define-SDL_Event-getter float (button y))